What is Decoherence?

a reply to: LesMisanthrope

First, you conceded you made a false statement. You said:

Obviously we do not know which path a particle takes if we do not measure it. I have a very limited understanding of Quantum Mechanics—I imagine way less than you—but even I know that because we do not know which path a particle takes, does not mean the particle does not exist.

Of course it means the particle doesn't exist. Where's the evidence that a particle exists before it's measured? Where's the evidence that a particle can be in two places at the same time? The wave function of a particle can be in superposition and this is represented by a qubit but there's no evidence that a a particle of matter exists before it's observed.

Much of your post shows a lack of understanding of quantum mechanics. It's always funny to me that people say things in a vacuum without any evidence. If the particle exists, how can it it be in two places at the same time? How can a particle of matter be in superposition?

Here's an example to illustrate this.

If you had a bag of marbles and 3 are blue and 2 are green, if these marbles are in a pure state, you have a marble that's 60% blue and 40% green. The materialist assumption is that matter must be in both states at the same time or in superposition. This is just an asinine assumption. There's no evidence that a particle exists let alone can be in both states at the same time.

The only reason you hear terms like weird and counterintuitive associated with quantum mechanics is because of the materialist assumption that particles must exist and therefore they must be in a state of superposition.

Both wave and particle like behavior can be explained by using the wave functions/state vectors alone. When you measure a marble it will be either blue or green. So how can you say the marble has an objective blue existence outside of your conscious perception that it's blue?

In it's pure state it's both blue and green, so the blue or green state you perceive isn't an objective material reality but a conscious observation of a green state.

If you're going to make the claim a particle exists independent of our observation you have to show how a material particle can be in a green state and blue state at the same time. You don't need a particle to exists, just the wave function which contains information about what states an observer can perceive when a measurement occurs.

You said:

You think some conscious observer existed before reality. But your logic requires that this conscious observer must also have been created by a conscious observer, and so on to infinity. In other words, your theory is groundless. It's turtles all the way down.

Why does my logic require that a conscious observer must also have been created by a conscious observer when I never claimed consciousness was an emergent property of the material brain?

This is what I mean by people saying these asinine things in a vacuum. Explain to me why if consciousness isn't an emergent property of the material brain why a conscious observer must create a conscious observer? You make no sense and this has nothing to do with anything I've said.

You said:

Again, explain to me how you can become conscious of an apple if there is not first an apple there to be conscious of, and I will agree with you.

EASY, YOU DON'T BECOME CONSCIOUS OF AN APPLE BUT A STATE THAT YOU PERCEIVE AS AN APPLE.

This is basic quantum mechanics.The only reason you can say that's an apple is because of your conscious perception that you're seeing an apple. Your conscious experience makes the state "real" not any material objective reality.

Adding the word "modern" to the title of the question completely changes it. In modern computers you need semiconductors, and the whole theory of solid state physics (band structures, doping, etc) is based on a foundation of quantum mechanics - since electrons in semiconducting solids behave in a manner that is more wave-like than particle-like, with each electron occupying its own distinct state. Making a semiconductor work well requires in depth understanding of these things. – Floris May 14 '14 at 13:07

Source
LM in actuality if it were not for QM you would not be able to respond at all to this thread.

Any thoughts?

edit on 10-6-2015 by Kashai because: Added content

originally posted by: neoholographic
Of course it means the particle doesn't exist. Where's the evidence that a particle exists before it's measured?

It may or may not. If a positron and electron suddenly pop into existence from the quantum foam, then they may not have existed or had a very short lifespan before you measured one or the other or both.

It is however possible to set up experiments where we can be fairly confident there are particles before we measure them.

Let's say we make a photon source that emits single photons as has been done for the double slit experiment. We measure the energy input to the photon emitter and see it's stable, and we can determine via measurement how many photons per minute it's emitting, let's say it's 30 photons per minute, or one every 2 seconds, on average. Let's say we do this for an hour.

Now we keep running the photon emitter, but simply remove the detector. Let's say it's outside and the photons are simply shooting off into space, at least we have reason to believe the same photon emitter that was emitting 30 photons a minute for the last hour is still emitting about 30 photons a minute. We have evidence to support this like many experiments confirming the conservation of energy, and we can continue to monitor the power input, measure the heat output, and say the difference between energy in and energy out as heat must be energy out as photons, which combined with the previous photon measurements is actually pretty good evidence.

Then without changing anything, we can put the photon detector back in place and see it's still detecting ~30 photons a minute.

To say the photons aren't still being emitted at the same approximate rate we measured before and after the interval where we made no measurements would violate conservation of energy principles which have a lot of evidence to support them, in fact many important studies rely on this conservation of energy principle including at places like the LHC at CERN.

Now you can say we don't know the position of unmeasured photons, and that would be true, but if you infer more than that from experimental results such as saying the unmeasured photons don't exist, I'm afraid you're distorting the implications of the experimental results. Unmeasured photons are simply unmeasured.

Where's the evidence that a particle can be in two places at the same time?

Well the evidence actually supports quantum mechanics theory which makes accurate predictions. There are several different possible interpretations of quantum mechanics and some say the particle takes two paths and some don't. We don't know which interpretation is correct, but all viable interpretations explain why it sort of looks the particle, or perhaps we should call it a "wavicle" seems to be taking two paths, even if that's not what's really happening. In the DeBroglie-Bohm theory, the particle is interpreted as taking one path only but this interpretation has an explanation of why it appears to take two paths in experiment.

a reply to: HotMale

I Don't Believe you exist when I'm not online. You are just a figment of my imagination.

originally posted by: Kashai

Adding the word "modern" to the title of the question completely changes it. In modern computers you need semiconductors, and the whole theory of solid state physics (band structures, doping, etc) is based on a foundation of quantum mechanics - since electrons in semiconducting solids behave in a manner that is more wave-like than particle-like, with each electron occupying its own distinct state. Making a semiconductor work well requires in depth understanding of these things. – Floris May 14 '14 at 13:07

Source
LM in actuality if it were not for QM you would not be able to respond at all to this thread.

Any thoughts?

So you mean to say without observation our electrons interact in the solid state hardware of a computer. Hmm that would mean that information is being passed from one system to another. Which means the act of information exchange is in fact an observation. Really not understanding why people aren't getting this.

a reply to: HotMale

To answer, if this reality is a program any feature in it is a part of the program.

then who programmed it?

a reply to: neoholographic

Why does my logic require that a conscious observer must also have been created by a conscious observer when I never claimed consciousness was an emergent property of the material brain?

so consciousness is a self-contained property requiring no physical host and no physical cause. please explain this.

a reply to: dragonridr


I get the part that prior to this discovery it was considered impossible and in perspective with LM's apple.

Further, without this discovery there would be no computers.

The fact we observe it now does not change that.

So I am wondering when some will come to terms with that fact as well.

To begin with, I’m not gonna get into a pissing match here with anyone over who’s reality is more real. I’ve got other things to do. However, there does seem to be a little confusion over some very basic concepts/terms in QM, and I’ll simply add my 2 cents.

First, I think the term “observer” may need some clarification. Observation is an action a physicist would call "work" taking place involving two or more events (the events being the subject(s) observed and the subject doing the observing) separated by a distance or difference of some kind. We naturally tend to consider observation as a biocentric activity, neglecting the fact that biological systems are composed of non-biological components... such as minerals and chemicals etc...

So, going with that and stretching the hell out of it, we could say that the non-biological elements of biological entities should also be considered as part of the act of observation. In which case, could we not attribute the act of observation to the non-biological components in part, if not entirely? After all, without these components the observation wouldn’t take place to begin with. Consequently, could it be further stated that the observed is, in turn, observing the observer... thus creating a "conversation" between the two?

We often metaphorically say things like a piece of equipment has "experienced" a certain degree of stress over it’s “lifetime”. In a like fashion, might we just as accurately say that this piece of equipment has “observed” a great deal of stress?

I realize this constitutes a colossal leap, if not downright betrayal, of logic. But then again, what does logic have to do with this? We’re talking quantum theory, after all. Just a thought...

Secondly, to answer the question posed in the OP, “What is Decoherence?”. I believe the conventional, accepted answer within the scientific mainstream is, “Who knows?” Frankly, it’s a concept of convenience and falls into the fuzzy zone. When (can’t remember who: Bohm or Zeh?) came up with the notion of decoherence it was basically an attempt to offer a physical explanation/mechanism for the collapse of the wavefunction. He wasn’t satisfied with the Copenhagen (instrumentalist) view, which focussed solely on the mathematical formalism of the process. Also, I think it was an attempt to explain the paradoxical problem of Schroedinger's cat by removing the need for an external observer.

Anyway, in this view the probabilistic behavior of a quantum system in superposition is a result of the system remaining isolated enough to maintain the coherence between the phase angles of it’s components. Decoherence is the physical process by which the system in superposition (quantum wavefunction) loses it’s coherence between the phase angles, resulting in a decoupling and “collapse” of the wave/function/system.

As helpful as that may be in (mis)understanding the process, it doesn’t really get at the essence of the phenomena. For instance, it doesn’t tell us precisely at which point the collapse takes place. There is no single, discrete point that we can identify in the process where the quantum probabilistic nature of reality instantly transitions into a final classical non-probabilistic (single) outcome. Also, decoherence doesn’t generate actual wave function collapse. It only provides an explanation for the observation of wave function collapse, as the quantum nature of the system "leaks" into the environment.

Bottom line is, the concept of decoherence remains a mystery to this day. Just can’t get there from here...

That’s my 2 cents. Hope you folks can finger it out. Could be a Nobel in it for you...

Have fun!

a reply to: netbound

So, going with that and stretching the hell out of it, we could say that the non-biological elements of biological entities should also be considered as part of the act of observation. In which case, could we not attribute the act of observation to the non-biological components in part, if not entirely? After all, without these components the observation wouldn’t take place to begin with. Consequently, could it be further stated that the observed is, in turn, observing the observer... thus creating a "conversation" between the two?

"observing" implies a certain amount of...note taking? rather than simply reacting to data out of reflex, like a cork in the water. water being the data, the cork being the particle. just because it follows the motion of the waves doesnt mean its actively tracking them and recording data. that implies consciousness, which is actually an assumed quality when the word "observation" is used because we are the loudest observers and therefore the strongest association...but matter doesnt process information like that. pure reflex, not a program. there is no act of deliberation, there is no memory, there is only riding the wave. perhaps on some level, we cause waves in the quantum fabric. this is not to say that the fabric is dependent on us anymore than oceans are dependent on ships. way too much romanticization going on here.

originally posted by: netbound
Secondly, to answer the question posed in the OP, “What is Decoherence?”. ...I think it was an attempt to explain the paradoxical problem of Schroedinger's cat by removing the need for an external observer.

...There is no single, discrete point that we can identify in the process where the quantum probabilistic nature of reality instantly transitions into a final classical non-probabilistic (single) outcome.

In the example of Schrodinger's Cat, there is. It's when the Geiger counter records the radioactive particle emission.

Critique of "Quantum Enigma: Physics encounters Consciousness"

von Neumann has treated a Geiger counter by a trivial wavefunction consisting of the superposition of only two states: whether it is in a “fired” or in an “unfired” state. This model of a Geiger counter, however, is incorrect, because it does not describe the essential property of such a detector, which is to be able to make a permanent record of an atomic event. Such a recording requires an irreversible process.

As I said you can put a camera in the box with the Geiger counter and cat and the camera will record when the Geiger counter detects a particle emission which ends up killing the cat. The Geiger counter isn't in some superposition of states or whatever you want to call it depending on which interpretation of quantum mechanics you use. Some people like von Neumann try to claim it is, but this is incorrect.

a reply to: Arbitrageur

No Consciousness?

No Box, no Camera, no radioactive material in the box, no justification whosoever as to a measurement problem.

No Knowledge.

a reply to: Kashai

Scrohdinger created the Cat thought experiment to express how absurd the interpretations his colleagues were offering were.

Instead of a Cat, put yourself in the box. To all outside observers you are in a superposition of alive and dead right, but I am sure you would argue from your vantage point, you will know for certain, that you will either be alive or dead, as time progresses. The truth occurs regardless of what the people outside of the box know about it.

a reply to: ImaFungi


Placing yourself in the box does not change the experiment as the observer in the experiment is to judge as to life or death.

If I know I am dead then I am not dead.

a reply to: Kashai
Can the hypothetical android "Data" from Star Trek have knowledge? Does it have consciousness?
Can the Geiger counter have knowledge of the radioactive decay event?
Where between the Geiger counter, the android or other AI and a human do you draw the line if there is one?

You can get into a game of semantics and philosophy that is beyond the scope of science. In some sense of the definition of knowledge the Geiger counter has knowledge of the decay event. That's what's relevant to this thread about decoherence.

The other thread "Quantum Experiment Confirms Reality Doesn't Exist Until Measured" is where the OP tries to make a case for this "consciousness required", but it's really just a tautology to say that only a conscious observer can make a conscious observation. It's like saying the reason my car is blue is because it was painted blue. While it may be true to make such claims they are far from useful. The Geiger counter doesn't need consciousness to record the decay event so consciousness is irrelevant to decoherence.

originally posted by: Kashai
a reply to: ImaFungi


Placing yourself in the box does not change the experiment as the observer in the experiment is to judge as to life or death.

If I know I am dead then I am not dead.

I didnt say it changed the experiment, thats why I used it.

You will know you are alive. When you know longer know you are alive, when you are dead, you will be dead. The people outside the box, with no information of what is going on inside, will not know the moment you die, you may not even know the moment you die, but in and as reality, there will be a continual stream of moments of you being alive, until the moment you die.

The concept of superposition, schrodinger was attempting to suggest with this thought experiment, was that the concept of superposition is purely a tool of ignorance; for people outside the box to say "we do not know, and we can not know what is going on inside the box, but if we consider all the possibilities and potentials, we can formulate a mathematical tool that will tell us the probability of what may occur, and in order to do that, we must consider the fact of our ignorance, that at any time we are not looking in the box, the cat is either alive or dead, we do not have enough information to assume one or the other, so we must assume the possibility of both"; this was then interpreted as; "the cat is alive and dead at the same time".


It is the same as tossing a single dice in the air and saying; we do not know what number will land facing up, so from our vantage point, there is a superposition of all the dice numbers landing up, and only once we look at the landed dice, will we collapse that superimposed wave function and yield the one number or another.

a reply to: Arbitrageur

I think they are trying to say something like this;

The best analogy I could think of;

poundingmillpress.com...

That our minds, or consciousness is like equal to those glasses; and different glasses see different things of reality, and some aspects of reality can only be seen with consciousness, and so they conclude that that means that consciousness is the only way in which those truths seen by consciousness 'actually exist'.

The observer effect mumbo jumbo has gotten way out of hand, and the way it is cheerleaded for years and years, nonstop, with extreme ignoring of the valid points against its unworthy claims, leads me to consider something fishy related to the perpetrators of the claims.

But anyway, yeah, its so simple to understand; however, one interesting thing, is classically, an observer doesnt need to 'tamper with the system to observe', a person doesnt shoot light out of their eyes and retrieve it, the light comes to the observer in the classical world. In the quantum world, the eyes cannot just observe the scale of experiments; so that is where the easy to get over hang up occurs; by equating the active methods of observation required to receive data in the quantum scales, to the passive methods of observation required to receive data in the classical scales.

That mix up, is exclaimed as then; if a person with eyes, looks at a quantum system, the quantum system is altered by the persons eyes looking.

When really, it is the mechanical eyes of equipment and devices, which does the looking, and how difficult it is to receive fundamental data about light, when light is usually used to receive fundamental data about all that is not light. So if there is a quantum system, a person with eyes looking at it or looking away, there will be no difference, besides the radiation coming off that person and perhaps any effects of wind and radiation created if the experiment is continuous in that the person looking away turns their head towards the quantum system.

Then to create eyes to see the quantum world with; where does the trouble come in, the small scales, the material of eyes radiating; I mean, substance enters an apparatus and needs to contact whatever 'eye' we build in order for us to 'know' anything about any experiment we do on that scale.

Substance goes in Side A. There is an eye at Side B. Which is interesting in its own right, because we dont like substance getting into our eye, we only like light in our eye, all we naturally, or most of what we naturally know about substance, is by the great incredible reflections off objects that then enter our eye. But in these experiments we try to collect more than light into our detector?

So the problems that can arise are, the energy that enters and radiates in and around the apparatus, and the nature of the energetic and geometric nature of the detector and how exactly it is designed to detect, how and what it is designed to detect, how certain it can be known how well and accurate it is detecting, and how much can be known about how much it can possibly be influencing the nature of what is detected.

But I guess all that should be easy enough; Enter X quantity quality substance, detect exactly X quantity quality substance.

originally posted by: dragonridr
a reply to: HotMale

I Don't Believe you exist when I'm not online. You are just a figment of my imagination.

Ok cool.

Just so you know, that is not what I have been saying. I have explained my theory multiple times, people keep coming back with arguments that don´t apply.

There is a universal reality that is the same for all of us, and we are all bound to the same rules. I said that the program only renders the parts of this reality that every "user" is experiencing, into matter. The rest of it is just data/code.

Arguments like "create a fish with your mind then" just show that people are not getting what others are saying.

a reply to: ImaFungi

The observer effect mumbo jumbo has gotten way out of hand, and the way it is cheerleaded for years and years, nonstop, with extreme ignoring of the valid points against its unworthy claims, leads me to consider something fishy related to the perpetrators of the claims.

Lol, facepalm.

I think someone does not know what the observer effect actually means.

In science, the term observer effect refers to changes that the act of observation will make on a phenomenon being observed. This is often the result of instruments that, by necessity, alter the state of what they measure in some manner. A commonplace example is checking the pressure in an automobile tire; this is difficult to do without letting out some of the air, thus changing the pressure. This effect can be observed in many domains of physics.

The observer effect on a physical process can often be reduced to insignificance by using better instruments or observation techniques.

en.wikipedia.org...



The observer effect is actually an argument being used by materialists against consciousness driven wave collapse.

And like I said before, experiments like the Quantum Eraser prove that it is not this effect that is causing the wave collapse.

In quantum eraser experments, a particle is detected by a measuring device. The wave collapses. One could argue that it is "the observer effect" that causes this, the physical interaction of the device with the particle, but this is wrong.

When the same happens, a particle is detected by a device, and which path info is available, but that information is "erased", or actually it is being made indeterminable, the wave does not collapse and it results in a wave/interference pattern.

How do you explain this? In both cases the particle has interacted with the measuring device and the physical setup of the experiment yet the wave does not collapse.

Like I said before, the availability of path info is the only variable here.

If the conscious observer has no role, then why does the availability of path info even matter? Pun intended.